1. Field of the Invention
The present invention relates to the technical field of wireless communications and, more particularly, to a transmitter and receiver apparatus for Multiple Input/Multiple Output MultiCarrier-Code Division Multiple Access (MIMO MC-CDMA) systems.
2. Description of Related Art
A new generation cellular mobile communication system has to provide wireless network applications with high-speed information transmission. Currently, it is known that MultiCarrier-Code Division Multiple Access (MC-CDMA) technique is one of the best solutions. CDMA is a core technique for the Third Generation Mobile Communication System, which applies Gold codes and OVSF (Orthogonal Variable Spreading Factor) codes to the system for allowing multiple users to concurrently transmit data on a same band.
Multi-carrier modulation is the principle of transmitting data by dividing a high-rate data stream into several parallel low-rate data streams onto individual carriers or subcarriers. By transmitting several symbols in parallel, the symbol duration is increased proportionately, which reduces the effects of ISI (Inter-Symbol Interference) caused by the dispersive Rayleigh-fading environment. By transmitting symbols onto subcarriers, frequency diversity is gained and thereby mitigating the effects of narrow band interference and frequency selective fading. Due to the advance of digital signal processing (DSP) and very large-scale integrated-circuit (VLSI), multi-carrier modulation is widely used in high-rate digital communications, such as digital broadcast, digital television and wireless local area network (WLAN). It is important in the present and future wireless multimedia communications.
In communication theory, multiple input/multiple output (MIMO) refers to radio links with multiple antennas at the transmitter and the receiver side. Given multiple antennas, the spatial dimension can be exploited to improve the performance of the wireless link.
In a typical MIMO MC-CDMA system, one multi-carrier modulator is connected to one transmitting antenna. That is, the transmitter has the same amount of multi-carrier modulators and transmitting antennas. The Inverse fast Fourier transform (IFFT) unit, which often occupies a large area in an Integrated Circuit (IC), is one of the most important, complicated and expensive units in a multi-carrier modulator. It means that multiple expensive IFFT units are necessary for a typical MIMO MC-CDMA system.